The invention relates to an internal axis rotary piston machine with meshing engagement between an outer rotor surrounded by a housing and having n +1 recesses arranged between engagement parts and an inner rotor with n engagement parts. When there is contact of the tooth-flank type between inside faces of the outer rotor and outside faces of the inner rotor, the two rotors rotate uniformly at a speed ratio of (n+1) : n, and working spaces are formed in the recesses of the outer rotor and move past inlet and outlet orifices of the housing.
An internal axis rotary piston machine of this type is known from U.S. Pat. No. 4,714,417 and is used especially as a compressor for supercharging motor vehicle engines. The housing consists of an essentially cylindrical part which has an intake channel and an exhaust channel and which is closed off at each of its axial ends by means of a housing cover. The inner rotor and the outer rotor are rotatable about mutually offset parallel axes, the speed ratio corresponding to the ratio of the number of recesses of the outer rotor to the number of engagement parts extending outwards from the axis of the inner rotor. For this purpose, there is a gear which, on the one hand, has a pinion fastened on the shaft of the inner rotor and meshing with an internally toothed wheel associated with the outer rotor. Such a gear connection is recommended in order to obtain the best possible sealing of the gap between the two rotors and prevent wear, although in principle the tooth-flank type of contact between the mutually associated faces of the two rotors can make the additional gear-wheel connection superfluous. The shaft of the inner rotor and also the outer rotor are mounted in the covers of the housing by means of suitable bearings, such as roller bearings. The outer rotor has inside faces forming radially inner corner regions which are the curve generatrices for outer peripheral faces of the inner rotor. The inner rotor also has corner regions which represent the curve generatrices of the inside faces of the outer rotor.